Tensile bond strength of self-etching versus total-etching adhesive systems under different dentinal substrate conditions

The use of acid etchants to produce surface demineralization and collagen network exposure, allowing adhesive monomers interdiffusion and consequently the formation of a hybrid layer, has been considered the most efficient mechanism of dentin bonding. The aim of this study was to compare the tensile bond strength to dentin of three adhesive systems, two self-etching ones (Clearfil SE Bond - CSEB and One Up Bond F - OUBF) and one total-etching one (Single Bond - SB), under three dentinal substrate conditions (wet, dry and re-wet). Ninety human, freshly extracted third molars were sectioned at the occlusal surface to remove enamel and to form a flat dentin wall. The specimens were restored with composite resin (Filtek Z250) and submitted to tensile bond strength testing (TBS) in an MTS 810. The data were submitted to two-way ANOVA and Tukey's test (p = 0.05). Wet dentin presented the highest TBS values for SB and CSEB. Dry dentin and re-wet produced significantly lower TBS values when using SB. OUBF was not affected by the different conditions of the dentin substrate, producing similar TBS values regardless of the surface pretreatments.

The effect of different light-curing units on tensile strength and microhardness of a composite resin

The aim of this study was to evaluate the influence of different light-curing units on the tensile bond strength and microhardness of a composite resin (Filtek Z250 - 3M/ESPE). Conventional halogen (Curing Light 2500 - 3M/ESPE; CL) and two blue light emitting diode curing units (Ultraled - Dabi/Atlante; UL; Ultrablue IS - DMC; UB3 and UB6) were selected for this study. Different light intensities (670, 130, 300, and 600 mW/cm2, respectively) and different curing times (20s, 40s and 60s) were evaluated. Knoop microhardness test was performed in the area corresponding to the fractured region of the specimen. A total of 12 groups (n=10) were established and the specimens were prepared using a stainless steel mold composed by two similar parts that contained a cone-shaped hole with two diameters (8.0 mm and 5.0 mm) and thickness of 1.0 mm. Next, the specimens were loaded in tensile strength until fracture in a universal testing machine at a crosshead speed of 0.5 mm/min and a 50 kg load cell. For the microhardness test, the same matrix was used to fabricate the specimens (12 groups; n=5). Microhardness was determined on the surfaces that were not exposed to the light source, using a Shimadzu HMV-2 Microhardness Tester at a static load of 50 g for 30 seconds. Data were analyzed statistically by two-way ANOVA and Tukey's test (p<0.05). Regarding the individual performance of the light-curing units, there was similarity in tensile strength with 20-s and 40-s exposure times and higher tensile strength when a 60-s light-activation time was used. Regarding microhardness, the halogen lamp had higher results when compared to the LED units. For all light-curing units, the variation of light-exposure time did not affect composite microhardness. However, lower irradiances needed longer light-activation times to produce similar effect as that obtained with high-irradiance light-curing sources.

Bond strength durability of direct and indirect composite systems following surface conditioning for repair

Purpose: This study evaluated the effect of surface conditioning methods and thermocycling on the bond strength between a resin composite and an indirect composite system in order to test the repair bond strength. Materials and Methods: Eighteen blocks (5 x 5 x 4 mm) of indirect resin composite (Sinfony) were fabricated according to the manufacturer's instructions. The specimens were randomly assigned to one of the following two treatment conditions (9 blocks per treatment): (1) 10% hydrofluoric acid (HF) for 90 s (Dentsply) + silanization, (2) silica coating with 30-Ìm SiOx particles (CoJet) + silanization. After surface conditioning, the bonding agent was applied (Adper Single Bond) and light polymerized. The composite resin (W3D Master) was condensed and polymerized incrementally to form a block. Following storage in distilled water at 37°C for 24 h, the indirect composite/resin blocks were sectioned in two axes (x and y) with a diamond disk under coolant irrigation to obtain nontrimmed specimens (sticks) with approximately 0.6 mm2 of bonding area. Twelve specimens were obtained per block (N = 216, n = 108 sticks). The specimens from each repaired block were again randomly divided into 2 groups and tested either after storage in water for 24 h or thermocycling (6000 cycles, 5°C to 55°C). The microtensile bond strength test was performed in a universal testing machine (crosshead speed: 1 mm/min). The mean bond strengths of the specimens of each block were statistically analyzed using two-way ANOVA (α = 0.05). Results: Both surface conditioning (p = 0.0001) and storage conditions (p = 0.0001) had a significant effect on the results. After 24 h water storage, silica coating and silanization (method 2) showed significantly higher bond strength results (46.4 ± 13.8 MPa) than that of hydrofluoric acid etching and silanization (method 1) (35.8 ± 9.7 MPa) (p < 0.001). After thermocycling, no significant difference was found between the mean bond strengths obtained with method 1 (34.1 ± 8.9 MPa) and method 2 (31.9 ± 7.9 MPa) (p > 0.05). Conclusion: Although after 24 h of testing, silica coating and silanization performed significantly better in resin-resin repair bond strength, both HF acid gel and silica coating followed by silanization revealed comparable bond strength results after thermocycling for 6000 times.

Influence of brush type as a carrier of adhesive solutions and paper points as an adhesive-excess remover on the resin bond to root dentin

Purpose: To evaluate the influence of the brush type as a earner of priming adhesive solutions and the use of paper points as a remover of the excess of these solutions on the push-out bond strength of resin cement to bovine root dentin. The null hypotheses were that brush type and the use of paper points do not affect the bond strength. Materials and Methods: The canals of 80 single-root bovine roots (16 mm in length) were prepared at 12 mm using the preparation drill (FRC Postec Plus, Ivoclar). Half of each root was embedded in acrylic resin and the specimens were divided into 8 groups, considering the factors brush type (4 levels) and paper point (2 levels) (n = 10): Gr 1: small microbrush (Cavi-Tip, SDI); Gr 2: Microbrush (Dentsply); Gr 3: Endobrush (Bisco); Gr 4: conventional brush (Bisco); Gr 5: Cavi-Tip (SDI) + paper points; Gr 6: Microbrush (Dentsply) + paper points; Gr 7: Endobrush (Bisco) + paper points; Gr 8: conventional brush (Bisco) + paper points. The root dentin was treated with a multistep total-etch adhesive system (All Bond 2). The adhesive system was applied using each microbrush, with and without using paper points. One fiber post was molded with addition silicon and 80 posts were made of resin cement (Duolink), The resin posts were luted (Duolink resin cement), and the specimens were stored for 24 h in water at 37°C. Each specimen was cut into 4 disk-shaped samples (1.8 mm in thickness), which were submitted to the push-out test. Results: The brush type (p < 0.0001) (small microbrush > microbrush = endobrush = conventional brush) and the use of paper points (p = 0.0001) (with > without) influenced the bond strength significantly (two-way ANOVA). The null hypotheses were rejected. Conclusion: The smallest brush (Cavi-Tip) and the use of paper points significantly improved the resin bond to bovine root dentin.

Influence of thermal and mechanical cycling on the flexural strength of ceramics with titanium or gold alloy frameworks

Objectives: The aim of this study was to evaluate the effect of thermal and mechanical cycling alone or in combination, on the flexural strength of ceramic and metallic frameworks cast in gold alloy or titanium. Methods: Metallic frameworks (25 mm × 3 mm × 0.5 mm) (N = 96) cast in gold alloy or commercial pure titanium (Ti cp) were obtained using acrylic templates. They were airborne particle-abraded with 150 μm aluminum oxide at the central area of the frameworks (8 mm × 3 mm). Bonding agent and opaque were applied on the particle-abraded surfaces and the corresponding ceramic for each metal was fired onto them. The thickness of the ceramic layer was standardized by positioning the frameworks in a metallic template (height: 1 mm). The specimens from each ceramic-metal combination (N = 96, n = 12 per group) were randomly assigned into four experimental fatigue conditions, namely water storage at 37 °C for 24 h (control group), thermal cycling (3000 cycles, between 4 and 55 °C, dwell time: 10 s), mechanical cycling (20,000 cycles under 10 N load, immersion in distilled water at 37 °C) and, thermal and mechanical cycling. A flexural strength test was performed in a universal testing machine (crosshead speed: 1.5 mm/min). Data were statistically analyzed using two-way ANOVA and Tukey's test (α = 0.05). Results: The mean flexural strength values for the ceramic-gold alloy combination (55 ± 7.2 MPa) were significantly higher than those of the ceramic-Ti cp combination (32 ± 6.7 MPa) regardless of the fatigue conditions performed (p < 0.05). Mechanical and thermo-mechanical fatigue decreased the flexural strength results significantly for both ceramic-gold alloy (52 ± 6.6 and 53 ± 5.6 MPa, respectively) and ceramic-Ti cp combinations (29 ± 6.8 and 29 ± 6.8 MPa, respectively) compared to the control group (58 ± 7.8 and 39 ± 5.1 MPa, for gold and Ti cp, respectively) (p < 0.05) (Tukey's test). While ceramic-Ti cp combinations failed adhesively at the metal-opaque interface, gold alloy frameworks exhibited a residue of ceramic material on the surface in all experimental groups. Significance: Mechanical and thermo-mechanical fatigue conditions decreased the flexural strength values for both ceramic-gold alloy and ceramic-Ti cp combinations with the results being significantly lower for the latter in all experimental conditions. © 2007 Academy of Dental Materials.

Influence of storage period and effect of different brands of acrylic resin on the dimensional accuracy of the maxillary denture base

The aim of this study was to evaluate the dimensional changes of denture bases made from different resins after different storage periods. For this purpose, 25 sets of plaster models/resin bases were prepared using 4 acrylic resins submitted to two types of polymerization: 1- QC-20 submitted to polymerization by microwave energy; 2- QC-20 submitted to polymerization by water hot bath; 3- Vipi Cril submitted to polymerization by water hot bath; 4- Vipi Wave submitted to polymerization by microwave energy; and 5- Onda Cryl submitted to polymerization by microwave energy. After polymerization, the specimens were sectioned for accuracy readings using a comparison microscope. Readings were taken at 3 points: the crests of the right (A) and left (B) ridges, and the median region of the palate, in 4 different periods. The data obtained were submitted to two-way ANOVA and Tukey's test at 5% significance level. The greatest distortions were found in the posterior palatal region of the base (M), with statistically significant difference (p<0.05) for the studied resins. All acrylic resins presented dimensional changes and the storage period influenced these alterations.

Changes on degree of conversion of dual-cure luting light-cured with blue LED

The indirect adhesive procedures constitute recently a substantial portion of contemporary esthetic restorative treatments. The resin cements have been used to bond tooth substrate and restorative materials. Due to recently introduction of the self-bonding resin luting cement based on a new monomer, filler and initiation technology has become important to study the degree of conversion of these new materials. In the present work the polymerization reaction and the filler content of dual-cured dental resin cements were studied by means of infra-red spectroscopy (FT-IR) and thermogravimetry (TG). Twenty specimens were made in a metallic mold (8 mm diameter × 1 mm thick) from each of 2 cements, Panavia® F2.0 (Kuraray) and RelyX™ Unicem Applicap (3M/ESPE). Each specimen was cured with blue LED with power density of 500 mW/cm 2 for 30 s. Immediately after curing, 24 and 48 h, and 7 days DC was determined. For each time interval 5 specimens were pulverized, pressed with KBr and analyzed with FT-IR. The TG measurements were performed in Netzsch TG 209 under oxygen atmosphere and heating rate of 10°C/min from 25 to 700°C. A two-way ANOVA showed DC (%) mean values statistically significance differences between two cements (p < 0.05). The Tukey's test showed no significant difference only for the 24 and 48 h after light irradiation for both resin cements (p > 0.05). The Relx-Y™ Unicem mean values were significantly higher than Panavia® F 2.0. The degree of conversion means values increasing with the storage time and the filler content showed similar for both resin cements. © 2009 Pleiades Publishing, Ltd.

Effect of light energy density on conversion degree and hardness of dual-cured resin cement

This study evaluated the effect of different light energy densities on conversion degree (CD) and Knoop hardness number (KHN) of RelyX ARC (RLX) resin cement. After manipulation according to the manufacturer's instructions, RLX was inserted into a rubber mold (0.8 mm X 5 mm) and covered with a Mylar strip. The tip of the lightcuring unit (LCU) was positioned in contact with the Mylar surface. Quartz-tungsten-halogen (QTH) and light-emitting diode (LED) LCUs with light densities of 10, 20 and 30 J/cm2 were used to light-cure the specimens. After light curing, the specimens were stored dry in lightproof containers at 37°C. After 24 hours, the CD was analyzed by FT-Raman and, after an additional 24-hours, samples were submitted to Knoop hardness testing. The data of the CD (%) and KHN were submitted to two-way ANOVA and the Tukey's test (α=0.05). QTH and LED were effective light curing units. For QTH, there were no differences among the light energy densities for CD or KHN. For LED, there was a significant reduction in CD with the light energy density set at 10 J/cm2. KHN was not influenced by the lightcuring unit and by its light energy density. © Operative Dentistry.

Evaluation of a new intraoral paralleling device for creating guiding planes: A pilot study

Aim: The aim of the study was to assess the accuracy of a new intraoral paralleling device for creating proximal guiding planes for removable partial dental prostheses. Methods and Materials: Thirty gypsum casts were divided into two groups in which the proximal surfaces of selected teeth were prepared using either a surveying device (Group 1) or the new ParalAB paralleling device (Group 2). In each cast guiding planes were prepared on the distal surface of the maxillary left canine (A), on the mesial and distal surfaces of the maxillary left second molar (B and C), and on the distal surface of the maxillary right canine (D). Each prepared surface formed an angle related to the occlusal plane that was measured five times and averaged by one operator using a tridimensional coordinate machine. Results: The mean guiding plane angles (± standard deviation) for the prepared surfaces were A=91.82° (±0.48°, B=90.47° (±0.47°, C=90.21° (±0.76°, and D=90.50° (±0.73°) for the dental surveyor (Group 1) and A=92.18° (±0.87°), B=90.90° (±0.85°), C=90.07° (±0.92°), and D=90.66° (±0.76°) for the ParalAB paralleling device (Group 2). A two-way ANOVA, Tukey's, and Levène's tests (at p<0.05) revealed statistically significant differences among surfaces prepared by both groups and that one surface Conclusions: The ParalAB device was able to prepare parallel surfaces and despite significant difference between groups, the ParalAB presented a small deviation from absolute parallelism and can be considered a valid method to transfer guide plans in the fabrication of removable partial dentures. Clinical Significance: The preparation of suitable guiding planes on abutment teeth during the fabrication of removable partial dentures is dependent on the ability of the operator and requires considerable chair time. When multiple teeth are involved, achieving parallelism between abutment surfaces can be technically challenging, especially in posterior regions of the mouth. The ParalAB prototype intraoral paralleling device can aid the clinician during the preparation of accurate guiding planes with a minimum degree of occlusal divergence. © 2010 Seer Publishing LLC.

Effect of phosphate-bonded investments on titanium reaction layer and crown fit

This study analyzed the reaction layer and measured the marginal crown fit of cast titanium applied to different phosphate-bonded investments, prepared under the following conditions (liquid concentration/casting temperature): Rema Exakt (RE) - 100%/237°C, 75%/287°C, Castorit Super C (CS)-100%/70°C, 75%/141°C and Rematitan Plus (RP)-100%/430°C (special to titanium cast, as the control group). The reaction layer was studied using the Vickers hardness test, and analyzed by two way ANOVA and Tukey's HSD tests (α = 0.05). Digital photographs were taken of the crowns seated on the die, the misfit was measured using an image analysis system and One-way ANOVA, and Tukey's test was applied (α = 0.05). The hardness decreased from the surface (601.17 VHN) to 150 μm (204.03 VHN). The group CS 75%/141°C presented higher hardness than the other groups, revealing higher surface contamination, but there were no differences among the groups at measurements deeper than 150 μm. The castings made with CS - 100%/70°C presented the lowest levels of marginal misfit, followed by RE -100%/237°C. The conventional investments CS (100%) and RE (100%) showed better marginal fit than RP, but the CS (75%) had higher surface contamination.

Effect of storage in artificial saliva and thermal cycling on Knoop hardness of resin denture teeth

Purpose: This study aimed to evaluate the effect of different storage periods in artificial saliva and thermal cycling on Knoop hardness of 8 commercial brands of resin denture teeth. Methods: Eigth different brands of resin denture teeth were evaluated (Artplus group, Biolux group, Biotone IPN group, Myerson group, SR Orthosit group, Trilux group, Trubyte Biotone group, and Vipi Dent Plus group). Twenty-four teeth of each brand had their occlusal surfaces ground flat and were embedded in autopolymerized acrylic resin. After polishing, the teeth were submitted to different conditions: (1) immersion in distilled water at 37 ± 2 °C for 48 ± 2. h (control); (2) storage in artificial saliva at 37 ± 2 °C for 15, 30 and 60 days, and (3) thermal cycling between 5 and 55 °C with 30-s dwell times for 5000 cycles. Knoop hardness test was performed after each condition. Data were analyzed with two-way ANOVA and Tukey's test (α= .05). Results: In general, SR Orthosit group presented the highest statistically significant Knoop hardness value while Myerson group exhibited the smallest statistically significant mean (P< .05) in the control period, after thermal cycling, and after all storage periods. The Knoop hardness means obtained before thermal cycling procedure (20.34 ± 4.45 KHN) were statistically higher than those reached after thermal cycling (19.77 ± 4.13 KHN). All brands of resin denture teeth were significantly softened after storage period in artificial saliva. Conclusion: Storage in saliva and thermal cycling significantly reduced the Knoop hardness of the resin denture teeth. SR Orthosit denture teeth showed the highest Knoop hardness values regardless the condition tested. © 2010 Japan Prosthodontic Society.

Effectiveness of rotary or manual techniques for removing a 6-year-old filling material

The aim of this study was to evaluate the effectiveness of manual and rotary instrumentation techniques for removing root fillings after different storage times. Twenty-four canals from palatal roots of human maxillary molars were instrumented and filled with gutta-percha and zinc-oxide eugenol-based sealer (Endofill), and were stored in saline for 6 years. Non-aged control specimens were treated in the same manner and stored for 1 week. All canals were retreated using hand files or ProTaper Universal NiTi rotary system. Radiographs were taken to determine the amount of remaining material in the canals. The roots were vertically split, the halves were examined with a clinical microscope and the obtained images were digitized. The images were evaluated with AutoCAD software and the percentage of residual material was calculated. Data were analyzed with two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) between the manual and rotary techniques for filling material removal regardless the ageing effect on endodontic sealers. When only the age of the filling material was analyzed microscopically, non-aged fillings that remained on the middle third of the canals presented a higher percentage of material remaining (p<0.05) compared to the aged sealers and to the other thirds of the roots. The apical third showed a higher percentage of residual filling material in both radiographic and microscopic analysis when compared to the other root thirds. In conclusion, all canals presented residual filling material after endodontic retreatment procedures. Microscopic analysis was more effective than radiographs for detection of residual filling material.

pH-changes during intracoronal bleaching: An in vivo study

Objectives: This study aimed to measure pH changes during 14 days intracoronal bleaching with hydrogen peroxide/sodium perborate and carbamide peroxide/sodium perborate. Materials and methods: Twenty patients presenting endodontically treated central maxillary incisors with color alterations were divided in two groups (n = 10): Group CP + SP: 37% carbamide peroxide + sodium perborate paste; Group HP + SP: 30% hydrogen peroxide + sodium perborate paste. The pH values were measured using a digital microprocessor at different times: Baseline, 2, 7 and 14 days. Data were analyzed with two-way ANOVA followed by Tukey's test (α = 0.05). Results: ANOVA showed p < 0.00 which indicated significant difference between the groups. The mean values (± sd) and the results of the Tukey's test were: HP + SP/14 days-7.98 (±0.58)a; HP + SP/7 days-8.59 (±0.18)b; HP + SP/2 days-8.83 (±0.32)bc; HP + SP/Baseline-8.83 (±0.01)bc; CP + SP/Baseline-8.89 (±0.01)bc; CP + SP/14 days-9.11 (±0.58)cd; CP + SP/7 days-9.54 (±0.16)de; CP + SP/2 days-9.66 (±0.08) de. The group HP + SP resulted in significantly lower pH values compared with group CP + SP. Conclusion: It can be concluded that both associations showed alkaline pH values; however, there was significant reduction in the pH values of the 30% hydrogen peroxide associated with sodium perborate after 14 days. Clinical Significance: The association of hydrogen peroxide and carbamide peroxide with sodium perborate paste presented alkaline characteristics during the 14-day evaluated period. Thus, regarding pH changes, both associations can be considered safe as intracoronal bleaching agents.

Silica coating on alumina ceramic: comparison of three chairside air-abrasion devices working for different times and distances.

This study evaluated, by scanning electron microscope (SEM) and EDS, the effect of different strategies for silica coating (sandblasters, time and distance) of a glass-infiltrated ceramic (In-Ceram Alumina). Forty-one ceramic blocks were produced. For comparison of the three air-abrasion devices, 15 ceramic samples were divided in three groups (N.=5): Bioart, Microetcher and Ronvig (air-abrasion parameters: 20 s at a distance of 10 mm). For evaluation of the time and distance factors, ceramic samples (N.=5) were allocated in groups considering three applied times (5 s, 13 s and 20 s) and two distances (10 mm and 20 mm), using the Ronvig device. In a control sample, no surface treatment was performed. After that, the micro-morphologic analyzes of the ceramic surfaces were made using SEM. EDS analyzes were carried out to detect the % of silica on representative ceramic surface. ANOVA and Tukey tests were used to analyze the results. One-way ANOVA showed the silica deposition was different for different devices (P=0.0054). The Ronvig device promoted the highest silica coating compared to the other devices (Tukey test). Two-way ANOVA showed the distance and time factors did not affect significantly the silica deposition (application time and distance showed no statistical difference). The Ronvig device provided the most effective silica deposition on glass-infiltrated alumina ceramic surface and the studied time and distance for air-abrasion did not affect the silica coating.

Effect of calcium hydroxide on pH changes of the external medium after intracoronal bleaching

Aim: This in vitro study evaluated the effect of calcium hydroxide on pH changes of the external medium after intracoronal bleaching. Materials and methods: A total of 50 extracted human premolars were prepared and filled with gutta-percha and endodontic sealer. The teeth were randomly divided into five groups according to the bleaching agents employed: (a) Sterile cotton pellet with distilled water (control group); (b) sodium perborate and distilled water; (c) sodium perborate and 10% carbamide peroxide; (d) sodium perborate and 35% hydrogen peroxide; (e) 35% hydrogen peroxide. The teeth were stored in vials containing distilled water and the pH values of the medium surrounding the teeth were analyzed. After 7-day storage, the bleaching agent was removed and replaced by calcium hydroxide, and the distilled water was changed, in which the teeth were kept stored for further 14 days. Measurement of pH of the external medium (distilled water) was performed 7 days after insertion of the bleaching agents, immediately, 7 and 14 days after insertion of the calcium hydroxide. Data were submitted to statistical analysis by the two-way ANOVA and Tukey,s test. Results: There were pH changes of the external medium at 7-day period after bleaching procedures. These results confirmed the diffusion of bleaching agents to the external medium. Conclusion: Calcium hydroxide increased the external medium pH and was effective for pH alkalinization after intracoronal bleaching. Clinical significance: Intracoronal bleaching of endodontically treated teeth may cause cervical root resorption. A possible explanation for this process is the passage of bleaching agents to the periodontal tissues yielding an inflammatory process. In an attempt to keep the neutrality of the periodontal pH, the calcium hydroxide has been recommended.Results of this study showed that this material should be always used after intracoronal bleaching.